jfs_debugfs

jfs_debugfs device

jfs_debugfs is a program which can be used to perform various low-level actions on a JFS formatted device.

device is the special file name corresponding to the actual device to be edited (e.g. /dev/hdb1).

jfs_debugfs must be run as root.

a[lter] <block> <offset> <hex_string>

replaces the data located at the <offset> of <block> with <hex_string>

<block> is the block number - given in decimal

<offset> is the offset within that block - given in hexadecimal

<hex_string> is an even-numbered string of hexadecimal digits to write to the disk

b[tree] <block> [<offset>]

* not implemented yet * displays one node of the btree located at <offset> of <block> and enters a subcommand mode to navigate the btree

SUBCOMMANDS: l => visit left sibling m => modify current node p => visit parent node r => visit right sibling [0-9] => visit the n'th child node x => exit subcommand mode

cb[blfsck]

displays the area used by ClearBadBlockList for communication with fsck

SUBCOMMANDS: m => modify entries x => exit subcommand mode

dir[ectory] <inode_number> [<file_set>]

displays the directory entries at <inode_number> and enters subcommand mode

<inode_number> is the directory's inode - given in decimal

<file_set> currently must be zero

SUBCOMMANDS: m => modify entries x => exit subcommand mode

d[isplay] [<block> [<offset> [<format> [<count>]]]]

displays <count> objects located at the <offset> of <block> in <format>

<block> is the block number - given in decimal

<offset> is the offset within <block> - given in hexadecimal

<format> is one of the following: a => ascii b => block allocation map d => decimal i => inode I => inode allocation map s => superblock x => hexadecimal X => extent allocation descriptor

<count> is the number of objects to display - given in decimal

dm[ap]

displays aggregate disk (block) map

SUBCOMMANDS m => modify map fields f => display free count t => display tree levels x => exit subcommand mode

dt[ree] <inode_number> [<file_set>]

displays root of the directory btree located at <inode_number> and enters a subcommand mode to navigate the btree

<inode_number> is the directory's inode - given in decimal

<file_set> currently must be zero

SUBCOMMANDS l => visit left sibling m => modify current node p => visit parent node (not parent directory) r => visit right sibling [0-9] => visit the n'th child node x => exit subcommand mode

fsckw[sphdr]

displays the header of the fsck workspace in the aggregate

SUBCOMMANDS: m => modify entries x => exit subcommand mode

h[elp] [<command>]

displays help for <command> if no command is given, all possible commands are displayed

ia[g] [<IAG_number>] [a | s | <file_set>]

displays IAG information for <IAG_number> and enters subcommand mode

<IAG_number> is given in decimal

a is to use the primary aggregate inode table

s is to use the secondary aggregate inode table

<file_set> currently must be zero

SUBCOMMANDS e => display/modify inode extents map m => modify IAG p => display/modify persistent map w => display/modify working map x => exit subcommand mode

i[node] [<inode_number>] [a | s | <file_set>]

displays inode information for <inode_number> and enters subcommand mode

<inode_number> is given in decimal

a is to use the primary aggregate inode table

s is to use the secondary aggregate inode table

<file_set> currently must be zero

SUBCOMMANDS a => display/modify inode's ACL m => modify inode x => exit subcommand mode

logs[uper]

displays the journal log superblock and enters subcommand mode

SUBCOMMANDS m => modify journal log superblock x => exit subcommand mode

q[uit]

exits jfs_debugfs

se[t] [<variable> <value>]

* not implemented yet * set user-defined <variable> to <value> if no arguments are given, displays all set variables

<variable> must begin with an alphabetic character

su[perblock] [p | s]

displays superblock data

p displays the primary superblock

s displays the secondary superblock

SUBCOMMANDS: m => modify entries x => exit subcommand mode

s2p[erblock] [p | s]

displays alternate superblock data

p displays the primary superblock

s displays the secondary superblock

SUBCOMMANDS: m => modify entries x => exit subcommand mode

u[nset] <variable>

* not implemented yet * deletes user-defined <variable>

xt[ree] <inode_number> [<file_set>]

displays root of the non-directory btree located at <inode_number> and enters a subcommand mode to navigate the btree

<inode_number> is the directory's inode - given in decimal

<file_set> currently must be zero

SUBCOMMANDS l => visit left sibling m => modify current node p => visit parent node (not parent directory) r => visit right sibling [0-9] => visit the n'th child node x => exit subcommand mode

If you find a bug in JFS or jfs_debugfs, please report it via the bug tracking system ("Report Bugs" section) of the JFS project web site:

http://jfs.sourceforge.net/

Please send as much pertinent information as possible, including the complete output of running jfs_fsck with the -v and -n options on the JFS device.

Barry Arndt  (barndt@us.ibm.com)
William Braswell, Jr.

jfs_debugfs is maintained by IBM.

See the JFS project web site for more details:
http://jfs.sourceforge.net/

jfs_fsck(8), jfs_mkfs(8), jfs_fscklog(8), jfs_logdump(8), jfs_tune(8),